31 4-17. Which of the following statements describes the method used in computers to subtract binary numbers? 1. R's complement the minuend and add to the subtrahend 2. Add the minuend and subtrahend and complement the sum 3. R's complement the subtrahend and add to the minuend 4. Subtract the subtrahend from the minuend and complement the difference Figure 4D.Adder/subtracter circuit. IN ANSWERING QUESTIONS 4-18 THROUGH 4-20, REFER TO FIGURE 4D. 4-18. What type of complement is performed by X-OR gates 1 and 2? 1. R's complement 2. Minuend complement 3. R's + 1 complement 4. Difference complement 4-19. Which of the following inputs is used for the least significant digit of the minuend? 1. A1 2. A23. B1 4. B24-20. What will be the output of (a) X-OR 2 and (b) X-OR 1 in the subtract mode with a subtrahend of 102? 1. (a) 0 (b) 0 2. (a) 0 (b) 1 3. (a) 1 (b) 0 4. (a) 1 (b) 1 4-21. Flip-flops are what type of multivibrators? 1. Astable 2. Monostable 3. Free running 4. Bistable 4-22. Flip-flops may NOT be used for which of the following operations? 1. Temporary storage 2. Subtraction 3. Division 4. Transfer of information 4-23. When, if ever, will the outputs Q and Q of an R-S flip-flop be the same? 1. When R and S are both LOW 2. When R is LOW and S is HIGH 3. When R is HIGH and S is LOW 4. Never